临界深度控制下的煤层瓦斯赋存规律差异性分析

Diversity Analysis of Coal Seam Gas Hosting Pattern under Critical Depth Control

多煤层开采,在增加矿区煤层资源量提高经济效益的同时,一定程度上也为研究区基础地质工作,特别是瓦斯赋存规律研究增加了难度。受多期地质构造影响,各煤层在空间展布规律、储层物性发育等存在明显差异,造成了瓦斯赋存规律的复杂性。为充分明确垂向煤层瓦斯赋存规律,以黑塘煤矿主采煤层为研究对象,以各主采煤储层物性特征为主要研究内容,基于等温吸附曲线、煤层瓦斯参数及地温测试资料分析,重点研究深度控制下各煤层瓦斯赋存规律并进行差异性分析,结果表明:在取样深度范围内,各煤层瓦斯含量随埋深变化趋势不同,浅部煤层与煤层埋深呈现递减趋势。相较于浅部煤层,深部煤层一定深度范围内,煤层瓦斯含量与埋深关系逐渐趋于正相关。当埋深达到800 m后,瓦斯含量和埋深关系进一步趋于复杂,表明该区域煤层大致以800 m为界存在"应力转折点"。同时,地质构造、水文地质条件及煤变质程度对煤层瓦斯垂向规律差异性的影响作用有限,地温局部异常引起垂向层段地温梯度差异性是研究区瓦斯含量存在"临界深度"的主控因素。

Although the development of multi - layer coal seams can increase mine area coal resources and promote economic benefits, but it is also increased difficulties on study area fundamental geological works, especially on gas hosting pattern study. Impacting from multi- staged structural movements, spatial extending pattern, reservoir physical property development of coal seams exist obvious differences, objectively caused complexity of coal seam gas hosting patterns. To fully reveal vertical coal seam gas hosting pattern, take the main mineable coal seams in the Heitang coalmine as subject investigated, their coal reservoir physical property features as main re- search objectives. Based on isothermal adsorption curves, coal seam gas parameters and geotemperature tested data analyses, focused on depth dependent coal seam gas hosting patterns and carried out diversity analysis. The result has shown that within the sampling depth range, trend of depth dependent coal seam gas content tend to be different, gas content of shallow part coal seams presents a trend of gradually decreasing. While for deep part coal seams, under a certain range of buried depth, the gas content and buried depth gradually tend to be positively correlated. After buried depth is reached 800m, the relation goes complicated a step further that is shown coal seams in the area roughly bounded by a depth 800m ＂stress turning point＂. At the same time, the impacts from geological struc- ture, hydrogeological condition and metamorphism degree of coal on coal seam gas vertical hosting pattern diversity are limited, thus geotemperature local anomaly caused vertical sector geothermal gradient diversity is the main controlling factor of the ＂critical depth＂ of coal seam gas content in the area.